Paul E. McKenney 6608c3a027 rcu/nocb: Reduce contention at no-CBs registry-time CB advancement
Currently, __call_rcu_nocb_wake() conditionally acquires the leaf rcu_node
structure's ->lock, and only afterwards does rcu_advance_cbs_nowake()
check to see if it is possible to advance callbacks without potentially
needing to awaken the grace-period kthread.  Given that the no-awaken
check can be done locklessly, this commit reverses the order, so that
rcu_advance_cbs_nowake() is invoked without holding the leaf rcu_node
structure's ->lock and rcu_advance_cbs_nowake() checks the grace-period
state before conditionally acquiring that lock, thus reducing the number
of needless acquistions of the leaf rcu_node structure's ->lock.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-08-13 14:35:49 -07:00
..
2019-05-28 09:05:23 -07:00